Can you please tell me the answer to 1.6cos(pie/0.8) in radians mode? Thank you in advance

1.6cos(pi/0.8) = -1.1313708498992 

this may be rong i do not know how to do that!

JUst use the calculator on this website:

cos(3.9269908169872415)*1.6 = -1.1313708498992